Definition 4 Let \(F_{X_1,\dots ,X_k}\)  be the cumulative distribution of the set of attributes
\(X_1,\dots ,X_k\) , and \(\mathbb {R}^k\)  their domain.
\(R[X_1,\dots ,X_k] \stackrel{d}{=}S[Y_1,\dots ,Y_k]\)  (they are identically distributed)
if [1]}:
\(\begin{split}F_{X_1,\dots ,X_k}(x_1,\dots ,x_k) = & F_{Y_1,\dots ,Y_k}(x_1,\dots ,x_k) \\& \forall (x_1,\dots ,x_k) \in \mathbb {R}^k\end{split}\) 

